In recent years digital projection systems have become common in simulation and visualization environments. These projection systems are often derived from those optimized for human-visible light projection. However, there are applications, such as night vision (NVIS) applications, where projection of images in non-visible spectra is desirable. Such non-visible images are generally viewable through the use of special equipment. An example of a non-visible image is an image projected using infrared (IR) light and hence, in these instances, the non-visible images are viewable in the simulation/visualization environment through the use of NVIS goggles and/or IR image detectors.
In some IR image projection systems, the visible and IR images are projected using two separate projectors, with associated image alignment problems. Another approach is to derive the IR images from the visible images in a single projector by filtering the projected visible images via a moveable filter placed between the light modulator and the projection lens. However, in these systems, the IR image is proportional to the intensity of a given visible color, for example the red component of the visible image. However, this approach is deficient in that not all IR reflectors/radiators inherently reflect and/or radiate red light (e.g. black surfaces). Hence, in a simulation/visualization environment, either the IR images are not properly simulated, or the red component of the visible images is too intense in regions where non-red IR reflectors/radiators are being simulated.